The present invention relates to a velocimeter, more particularly the present invention relates to a velocimeter made of discrete disk probes.
Present methods for measuring multiple components of velocity can be divided into two broad classes: accurate, expensive, laboratory-type instruments, and robust (but less accurate), inexpensive, instruments.
Into the first class would fall devices such as hot wire anemometers see for example, Comte-Bellot, G. 1976: Hot wire anemometry. Annual Review of Fluid Mechanics Vol. 8, 209-231; or Perry, E. 1982: Hot wire anemometry. Oxford: Clarendon Press: laser Doppler velocimeters, see for example, Drain, L. E. 1980: The Laser Doppler technique. New York: Wiley or Drain, L. E. 1980: The Laser Doppler technique. New York: Wiley: or particle image velocimeters see for example, Adrian, R. J. 1991: Particle imaging techniques for experimental fluid mechanics. Annual Review of Fluid Mechanics Vol. 23, 261-304 or Grant, 1. 1997: Particle image velocimetry: A review. Journal of Mechanical Engineering Science 211, 55-76, and a host of others. These devices are characterized by excellent accuracy (typically, velocities can be measured to within 1%) but high cost ($10 k-$100 k+) and comparatively poor durability. Their high cost and poor durability in general limit these devices to use in a controlled environment like a laboratory; they are rarely used in an industrial or field work setting.
The class of robust, inexpensive instruments would include cup, propeller, and vane anemometers see Wyngaard, J. C. 1981: Cup, propeller, vane, and sonic anemometers in turbulence research. Annual Review of Fluid Mechanics Vol. 13, 399-423: claw probes, yaw head probes, and five-hole and seven-hole probes, see for example, Wyngaard, J. C. 1981: Cup, propeller, vane, and sonic anemometers in turbulence research Annual Review of Fluid Mechanics Vol.13, 399-423; Chue, S. H. 1975: Pressure probes for fluid measurement. Progress in Aerospace Science Vol.16, 147-223; Zilliac, G. G. 1993: Modelling, calibration, and error analysis of seven hole pressure probes. Experiments in Fluids Vol. 14, 104-120; and Everett, K. N., Gerner, A. A., and Durston, D. A. 1983: Seven-hole cone probes for high angle flow measurement: theory and calibration. AIAA Journal Vol. 21, 992. In general, these devices are reliable and reasonably accurate (directions to xc2x11xc2x0 and velocities to xc2x11%), but can accurately measure only mean flow velocities within xc2x170xc2x0 of a known flow direction (see Chue and Zilliac referred to above).
Recently, Rediniotis and Kinser (see Rediniotis, O. K. and Kinser, R. E. 1998: Development of a nearly omnidirectional velocity measurement pressure probe. AIAA Journal Vol. 36, 1854-1860) have developed a probe using 18 holes over the surface of a sphere. Although this probe is nearly omni-directional (cone angles  greater than 90 degrees), and is apparently accurate for the reported conditions, it should be noted that calibration of this device is complex due to the large number of pressure taps and the complex flow regimes around a sphere that occur at various Reynolds numbers.
International Application no WO 91/03739 published Mar. 21, 1991 discloses a flow speed meter for channels or tunnels that uses a plate oriented with its major side surfaces perpendicular to the direction of flow and measures the differential pressure between opposite sides to determine the flow velocity.
To the Applicants"" knowledge, prior to the present invention no device was available that will robustly and economically measure velocities particularly 2 dimensional (2D) and 3 dimensional (3D) velocities in highly 2D or 3D flow.
It is an object of the invention to provide a disk probe for measuring fluid flow velocities. It is a further object of the invention to provide a multiple disk probe capable of robustly and economically measuring velocities, particularly 3D velocities in highly 3D flow.
Broadly, the present invention relates to a device for measuring fluid flow comprising a substantially circular disk having a pair of opposed substantially parallel side faces, pressure sensor means at the center of each of said pair of faces to sense pressure at said center of each said face thereby to provide a substantially symmetrical disk probe.
Preferably said outer faces are connected together at their outer peripheries by a beveled edge symmetrical relative to said pair of faces.
Preferably said disk has a diameter D greater than 3 mm and preferably between 3 to 40 mm.
Preferably said disk has a thickness t measured between said parallel faces of t less than xc2xd the diameter D of said disk.
Preferably said beveled edge is defined by bevel surfaces extending at bevel angle xcex2 in the range of 45 to 80xc2x0.
Preferably said pressure sensor means comprises a pressure transducer for sensing pressure difference between said centers of said pair of faces.
Preferably said pressure sensor comprises a pair of pressure taps positioned at said center of each of said pair of faces.
Preferably said device comprises a plurality of said disks arranged with said pair of faces of each of said disks orthogonal to said pair of faces of other disks of said plurality of disks.
Preferably said device comprises two said disks.
Preferably said device comprises three said disks.
Preferably said device includes a pressure transducer for each said disk and a computer programmed to compute velocity and direction of flow of said fluid.
Preferably said device comprises a pair of said orthogonal disks arranged in orthogonal relationship with the axis of a pitot-static probe.